Method for removing iron ions from galvanizing flux solution

ABSTRACT

A method for removing iron ions from galvanizing flux solution includes adding zinc chloride and ammonium chloride to a solvent in a preparing tank to prepare a first galvanizing flux solution which is transferred to a treatment tank, immersing an iron/steel piece in the first galvanizing flux solution to dissolve part of the surface to form iron ions, adding oxygen-rich gas to the first galvanizing flux solution to oxidize the iron ions to form a second galvanizing flux solution containing iron oxide precipitation, filtering the second galvanizing flux solution by a multilayer filter to form a third galvanizing flux solution without iron oxide or with low content of iron oxide, transferring the third galvanizing flux solution back to the treatment tank, and repeating the above steps by immersing another iron/steel piece in the first galvanizing flux solution so as to continuously remove iron ions generated.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to a method for removing iron ions from flux solution, more specifically to a method for removing iron ions from galvanizing flux solution by oxidizing iron ions with oxygen-rich gas to form iron oxide precipitation without changing the content of zinc chloride and ammonium chloride in the galvanizing flux solution.

2. The Prior Arts

Traditionally, using the galvanizing flux solution to wet the surface of an iron piece is a common pre-treatment for hot-dip galvanizing, which facilitates the formations of the iron-zinc alloy layer with excellent corrosive-resistant property in the subsequent process so as to protect the iron piece from oxidations.

In the wetting process, the surface of the iron piece is partly dissolved in the galvanizing flux solution to form iron ions, which may cause the molten zinc to form unwanted zinc ash in the latter hot-dip galvanizing process. As a result, the property of the iron-zinc layer is seriously deteriorated and the ability of anti-corrosions is greatly weakened. In the prior arts, one of the solutions is to frequently inspect the iron ions content in the galvanizing flux solution and remove the zinc ash. One specific means is that hydrogen peroxide is added to the galvanizing flux solution to cause iron ions to precipitate by redox reactions, and then the precipitation, that is, iron oxide, is filtered and removed. Therefore, removing iron ions from the galvanizing flux solution is attained.

However, one of the shortcomings in the prior arts is that the efficiency of removing iron ions is only 40 to 60%. Also, zinc chloride and ammonium chloride in the galvanizing flux solution, is reduced because of adding hydrogen peroxide in liquid form, and a great amount of zinc chloride and ammonium chloride is needed to add to the galvanizing flux solution to maintain the wetting effect on the iron piece. As a result, the fabricating cost is increased. It thus needs to provide a method for removing iron ions from galvanizing flux solution without influence on the concentrations of zinc chloride and ammonium chloride, thereby overcoming the above problems in the prior arts.

SUMMARY OF THE INVENTION

The primary object of the present invention is to provide a method for removing iron ions from galvanizing flux solution for wetting the surface of an iron/steel piece so as to facilitate the formations of zinc layer in the subsequent hot-dip galvanizing. The method of the present invention generally comprises preparing a galvanizing flux solution by adding zinc chloride and ammonium chloride to a solvent in a treatment tank, immersing the iron/steel piece into the galvanizing flux solution so as to dissolve part of the surface of the iron/steel piece; adding oxygen-rich gas to the galvanizing flux solution to oxidize the iron ions to form iron oxide precipitation, extracting and filtering the galvanizing flux solution from the treatment tank by a multilayer filter to separate iron oxide; transferring the filtered galvanizing flux solution back to the treatment tank; returning back to the above step of immersing another iron/steel piece into the galvanizing flux solution; and repeating the subsequent steps.

The present invention continuously removes the iron ions generated by immersing the iron/steel piece into the galvanizing flux solution, and also maintains the content of zinc chloride and ammonium chloride without replenishing additional zinc chloride and ammonium chloride. Accordingly, the wetting effect on the surface of the iron/steel piece is ensured. It is possibly applicable to the subsequent process of hot-dip galvanizing to coat the zinc layer. In particular, it greatly helps the iron-zinc reactions to generate the iron-zinc alloy layer with excellent corrosive-resistant property, which protects the iron/steel piece from further oxidation.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention can be understood in more detail by reading the subsequent detailed descriptions in conjunctions with the examples and references made to the accompanying drawings, wherein:

FIG. 1 is a flowchart showing the method for removing iron ions from galvanizing flux solution according to the present invention; and

FIG. 2 is a systematic view illustrating the method according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention may be embodied in various forms and the details of the preferred embodiments of the present invention will be described in the subsequent content with reference to the accompanying drawings. The drawings (not to scale) show and depict only the preferred embodiments of the invention and shall not be considered as limitations to the scope of the present invention. Modifications of the shape of the present invention shall to be considered to be within the spirit of the present invention.

Please refer to both FIGS. 1 and 2 for detail description of the present invention. FIG. 1 is a flowchart showing the method for removing iron ions from galvanizing flux solution according to the present invention, and FIG. 2 is a systematic view illustrating the method of the present invention. As shown in FIGS. 1 and 2, the method of the present invention starts at the step S10 by adding zinc chloride and ammonium chloride into a solvent in the preparing tank 10 to prepare the first galvanizing flux solution F1, and the first galvanizing flux solution F1 is further transferred to the treatment tank 20.

The above first galvanizing flux solution F1 can be prepared by use of the stirring device to speed up the dissolving process of zinc chloride and ammonium chloride. The stifling device may comprise a plurality of stirring rods or blades. Also, the stirring device is preferably formed of plastic or ceramic material. The compositions of zinc chloride and ammonium chloride in weight ratio is within a range of 1:1.05 to 1:1.55. The solvent is deionized water or purified water.

It should be noted that the preparing tank 10 can serve as the treatment tank 20 in another embodiment of the present invention. In other words, the treatment tank 20 is the preparing tank 10.

Next, the step S20 is to immerse at least one iron/steel piece 30 into the first galvanizing flux solution F1 in the treatment tank 20 such that part of the surface of the iron/steel piece is dissolved in the first galvanizing flux solution F1 to form iron ions. As a result, the wetting effect on the surface of the iron/steel piece 30 is specifically implemented.

The step S30 is then performed by adding oxygen-rich gas G to the first galvanizing flux solution F1 to oxidize the iron ions and form iron oxide precipitation. Thus, the second galvanizing flux solution F2 containing iron oxide is generated.

The oxygen-rich gas G may comprise at least one of nitrogen oxide, high purified oxygen gas and ozone, and the high purified oxygen gas contains more than 50% oxygen. It is preferred that the oxygen-rich gas G is injected into the bottom of the treatment tank 20 such that the resulting bubbles float and react with the iron ions. Additionally, some mixing device (not shown), like stirring rod, is implemented to accelerate the oxidations reactions of the iron ions.

Then in the step S40, the second galvanizing flux solution F2 is extracted from the treatment tank 20 by a water pump motor (not shown). Also, a multilayer filter 40 is employed to filter the second galvanizing flux solution F2 and separate iron oxide precipitation. Then, the third galvanizing flux solution F3 without iron oxide or with low content of iron oxide is generated.

Finally, the third galvanizing flux solution F3 is transferred back to the treatment tank 20 in the step S50 and then the step S20 is repeated such that another iron/steel piece is then processed. In other words, the steps S20˜S50 as mentioned above are repeated for other iron/steel pieces to be processed.

From the above-mentioned, one aspect of the present invention is that the concentration of zinc chloride and ammonium chloride in the galvanizing flux solution is well maintained without adding additional zinc chloride and ammonium chloride so as to ensure the wetting effect on the surface of the iron/steel piece. Therefore, the method of the present invention is very applicable to the subsequent hot-dip galvanizing process to help the iron-zinc reactions to form a layer of anti-corrosive iron-zinc alloy, and the iron/steel piece is protected from oxidations.

Although the present invention has been described with reference to the preferred embodiments, it will be understood that the invention is not limited to the details described thereof. Various substitutions and modifications have been suggested in the foregoing descriptions, and others will occur to those of ordinary skill in the art. Therefore, all such substitutions and modifications are intended to be embraced within the scope of the invention as defined in the appended claims. 

What is claimed is:
 1. A method for removing iron ions from galvanizing flux solution, comprising: adding zinc chloride and ammonium chloride to a solvent in a preparing tank to prepare a first galvanizing flux solution, which is then transferred to a treatment tank; immersing at least one iron/steel piece in the first galvanizing flux solution such that part of a surface of the iron/steel piece is dissolved in the first galvanizing flux solution to generate iron ions so as to wet the surface of the iron/steel piece; adding oxygen-rich gas to the first galvanizing flux solution to oxidize the iron ions to form a second galvanizing flux solution containing iron oxide precipitation; filtering the second galvanizing flux solution by a multilayer filter to separate iron oxide and form a third galvanizing flux solution without iron oxide or with low content of iron oxide; transferring the third galvanizing flux solution back to the treatment tank; and repeating the above steps by immersing another iron/steel piece in the first galvanizing flux solution so as to continuously remove iron ions generated.
 2. The method as claimed in claim 1, wherein a weight ratio of zinc chloride to ammonium chloride in the first galvanizing flux solution is within 1:1.05 and 1:1.55, and the solvent is deionized water or pure water.
 3. The method as claimed in claim 1, wherein the preparing tank serves as the treatment tank.
 4. The method as claimed in claim 1, wherein the oxygen-rich gas comprises at least one of nitrogen oxide, high purified oxygen gas and ozone, and the high purified oxygen gas contains more than 50% oxygen. 